A common method of treating temporary or chronic pain is by application of heat to the afflicted area. Such heat treatments are used as a means of therapy for conditions which include aches, stiffness in muscles and joints, nerve pain, rheumatism and the like. These treatments include the use of whirlpools, hot towels, hydrocollators, heating pads and elastic compression bands. Many of these devices employ reusable thermal packs containing, e.g., water and microwaveable gels. In general, such devices which require the thermal source to be replenished are inconvenient to use. Further, many of these thermal units or devices do not provide long lasting heat and also do not maintain a consistent temperature over long periods of time. Depending on the length of exposure, the skin temperature needs to be maintained from about 35.degree. C. to about 55.degree. C., preferably from about 36.degree. C. to about 45.degree. C., more preferably from about 37.degree. C. to about 43.degree. C., and most preferably from about 38.degree. C. to about 42.degree. C., to achieve the desired therapeutic benefits.
The beneficial therapeutic effects from this administration of heat diminish after the heat source is removed. Therefore, depending on the temperature, it is desirable to provide a sustained heat source to the afflicted area for as long as possible, i.e., from about twenty minutes to about twelve hours, preferably from about four hours to about twelve hours, most preferably from about eight hours to about twelve hours. Disposable heat packs based on iron oxidation, such as those described in U.S. Pat. Nos. 4,366,804, 4,649,895, 5,046,479 and Re. 32,026, are known. However, such devices have proven not totally satisfactory because many of these devices are bulky, cannot maintain a consistent and controlled temperature, and have unsatisfactory physical dimensions, which hinder their effectiveness. Specifically, such devices cannot be easily incorporated into pads which can comfortably conform to various body contours, and hence, they deliver short duration, inconsistent, inconvenient and/or uncomfortable heat application directly to the body.
The present inventors have discovered disposable thermal body pads comprising one or more thermal packs having a unified structure, wherein each thermal pack has at least one continuous layer of a semirigid material which is sufficiently rigid in specific areas of the thermal pack, yet which softens in between such areas when heated during use, preferably comprising a coextruded film of polypropylene and EVA. The thermal pack or packs also comprise a plurality of individual heat cells, which typically comprise an exothermic composition, preferably comprising a specific iron oxidation chemistry and having specific physical dimensions and fill characteristics, spaced apart and fixedly attached across the thermal pack. Active heat cells, that is, heat cells having a temperature of from about 39.degree. C. to about 60.degree. C., preferably from about 40.degree. C. to about 48.degree. C., more preferably from about 41.degree. C. to about 47.degree. C., most preferably from about 42.degree. C. to about 45.degree. C., preferably soften narrow portions of the continuous layer or layers of semirigid, material which immediately surround the heat cells. All remaining portions of the continuous layer or layers which surround the softened portions remain more rigid. The narrow, softened portions act as hinges between each heat cell and the remaining, cooler, more rigid portions, bending preferentially more than either the heat cell or the more rigid portions. This results in thermal packs which possess sufficient rigidity to maintain structural support of the heat cells, to prevent unacceptable stretching of structures of the continuous layer or layers during processing or use, and to ensure child resistance, while still maintaining good overall drape characteristics when heated. The thermal pack or packs, when incorporated into the disposable thermal body pads of the present invention, provide uniform heat coverage by having excellent conformity with the user's body.
It is therefore an object of the present invention to provide disposable thermal body pads comprising one or more thermal packs having a unified structure of at least one continuous layer of semirigid material, which has different stiffness characteristics over a range of temperatures, and a plurality of individual heat cells, which provide a controlled and sustained temperature and which reach their operating temperature range relatively quickly. The heat cells are spaced apart and fixedly attached across the thermal pack.
It is a further object of the present invention to provide disposable thermal body pads having good overall drapability while maintaining sufficient rigidity to maintain structural support of the heat cells and prevent unacceptable stretching of the continuous layer or layers during processing or use.
It is a still further object on the present invention to provide disposable thermal body pads which adapt to a wide variety of body contours providing consistent, convenient and comfortable heat application while ensuring child resistance.
It is another object of the present invention is to provide disposable thermal body pads comprising a means for attaching the thermal body pad to a user's clothing so that the opposite side of the thermal body pad may be worn directly against the user's skin.
These objectives and additional objectives will become readily apparent from the detailed description which follows.